1. Field of the Invention
The present invention relates to an expandable and crosslinkable elastomeric material with improved fire retardant properties and low smoke generation, the process for manufacturing of such material and the use of such material.
2. Description of the Background Art
Fire retardancy and the issues conjugated herewith play an important role in the field of elastomer development. Many efforts have been taken to select and produce fire retardant rubber bases, with prominent examples, such as PVC or chloroprene (CR). The latter has often been used as fire retardant adhesive (e.g. JP 11346416), coating (e.g. DE 2453238) or as impregnation for the same purpose (e.g. JP 62167334). An extraordinary challenge is to render elastomeric foams fire retardant or at least less flammable as the air included in the foam cells and the thin cell walls will accelerate flame spread. Chloroprene has been used also here to reduce flammability, such as impregnation of existing foams (e.g. GB 977929) or as foamed CR latices, emulsions and such (e.g. JP 61272248, JP 10060151, the latter also said to be suitable for thermal insulation). These methods, however, will lead to non-flexible materials and/or mechanically weak compounds. Foamed pure rubbers with better mechanical and general properties in CR are quite rare; in some cases the CR (among other polymers and fillers) is just used as a massive rubber base and the foam is only formed in contact with flame (so-called intumescences, as in DE 4135678, UA 61419, UA 78131), in other cases the manufacturing of the foam is very complicated and costly, as it is done using polymerization (JP 6041341, however, flame retardant properties are not even mentioned) or by using both a complicated formulation and expansion method (JP 60186543 and JP 60186544; based on critical chemicals such as isocyanate).
It is known from the above stated patent literature that chloroprene containing formulations can be used to improve flame resistance properties, but those formulations generate high levels of smoke which is seen as the most severe threat for humans in case of fire. Even less works have been done on flame retardant insulating materials, especially thermal insulation compounds: JP 10077478 mentions a compound (where CR is a possible ingredient) which will give an insulation effect against flame spread during fire by formation of water vapour, whereas JP 1182030 mentions a foamed CR for wetsuits achieving the insulation properties by low-conductive filler. However, a suitable flame retardant flexible foam material for industrial as well as for general (e.g. building) insulation and shielding/damping purposes can not be obtained by any of the above mentioned state of the art technologies, especially in regard to the fact that flame retardant and protective properties are required and get more severe in all public sectors: new challenges have come up such as the harmonization of European standards concerning building and construction insulation (EN 13823, “Euroclasses”); these standards do not only require a general flame retardancy, but include severe testing conditions (“SBI round corner test”) and add additional obstacles for norm fulfillment by introducing parameters such as flame and smoke generation and smoke density.